MongoDB tree-shaped structure notation

Http://docs.mongodb.org/manual/tutorial/model-tree-structures/MongoDB Five kinds of tree-shaped structure notation

First type: Parent link structure

db.categories.insert( { _id: "MongoDB", parent: "Databases" } )db.categories.insert( { _id: "dbm", parent: "Databases" } )db.categories.insert( { _id: "Databases", parent: "Programming" } )db.categories.insert( { _id: "Languages", parent: "Programming" } )db.categories.insert( { _id: "Programming", parent: "Books" } )db.categories.insert( { _id: "Books", parent: null } )

Characteristics:

1. Quick Get parent node:

   Db.categories.findOne ({_id: "MongoDB"}). Parent

2. Easy to create parent node index

   Db.categories.ensureIndex ({parent:1})

3. Get son node by querying parent node

   Db.categories.find ({parent: "Databases"})

4. Multiple queries are required to retrieve subtrees.

Second Type: sub-link structure

db.categories.insert( { _id: "MongoDB", children: [] } )db.categories.insert( { _id: "dbm", children: [] } )db.categories.insert( { _id: "Databases", children: [ "MongoDB", "dbm" ] } )db.categories.insert( { _id: "Languages", children: [] } )db.categories.insert( { _id: "Programming", children: [ "Databases", "Languages" ] } )db.categories.insert( { _id: "Books", children: [ "Programming" ] } )

Characteristics:

1. Quick Get son node

   Db.categories.findOne ({_id: "Databases"}). Children

2. Easy to create child node index

   Db.categories.ensureIndex ({children:1})

3. Get parent node by querying son node

   Db.categories.find ({children: "MongoDB"})

4. Suitable for storing storage graphs, one node may have multiple parents.

The third type: ancestor queue structure

db.categories.insert( { _id: "MongoDB", ancestors: [ "Books", "Programming", "Databases" ], parent: "Databases" } )db.categories.insert( { _id: "dbm", ancestors: [ "Books", "Programming", "Databases" ], parent: "Databases" } )db.categories.insert( { _id: "Databases", ancestors: [ "Books", "Programming" ], parent: "Programming" } )db.categories.insert( { _id: "Languages", ancestors: [ "Books", "Programming" ], parent: "Programming" } )db.categories.insert( { _id: "Programming", ancestors: [ "Books" ], parent: "Books" } )db.categories.insert( { _id: "Books", ancestors: [ ], parent: null } )

Characteristics:

1. Get Ancestors Fast

   Db.categories.findOne ({_id: "MongoDB"}). Ancestors

2. Easy to create ancestor node index

   Db.categories.ensureIndex ({ancestors:1})

3. retrieving descendants by querying ancestors

   Db.categories.find ({ancestors: "Programming"})

4. Ancestor mode is slightly slower than materialized path mode

Fourth type: materialized path structure

db.categories.insert( { _id: "Books", path: null } )db.categories.insert( { _id: "Programming", path: ",Books," } )db.categories.insert( { _id: "Databases", path: ",Books,Programming," } )db.categories.insert( { _id: "Languages", path: ",Books,Programming," } )db.categories.insert( { _id: "MongoDB", path: ",Books,Programming,Databases," } )db.categories.insert( { _id: "dbm", path: ",Books,Programming,Databases," } )

Characteristics:

1. Retrieving sorting by query

   Db.categories.find (). Sort ({path:1})

2. Quick Find child nodes

   Db.categories.find ({path:/^,books,/}) Db.categories.find ({path:/^,books,/})

3. To create an index for a path

   Db.categories.ensureIndex ({path:1})

Fifth: Set model

db.categories.insert( { _id: "Books", parent: 0, left: 1, right: 12 } )db.categories.insert( { _id: "Programming", parent: "Books", left: 2, right: 11 } )db.categories.insert( { _id: "Languages", parent: "Programming", left: 3, right: 4 } )db.categories.insert( { _id: "Databases", parent: "Programming", left: 5, right: 10 } )db.categories.insert( { _id: "MongoDB", parent: "Databases", left: 6, right: 7 } )db.categories.insert( { _id: "dbm", parent: "Databases", left: 8, right: 9 } )

Characteristics:

1. Quickly get child nodes

   var databasecategory = Db.categories.findOne ({_id: "Databases"}); Db.categories.find ({left: {$gt: Databasecategory.left}, right: {$lt: Databasecategory.right}});

2. Content modification is inefficient for static trees.

MongoDB tree-shaped structure notation